Radio Waves

Radio waves are a type of
electromagnetic radiation with wavelengths in the electromagnetic spectrum
longer than infrared light. Like all other electromagnetic waves, they
travel at the speed of light. Naturally-occurring radio waves are made by
lightning, or by astronomical objects. Artificially-generated radio waves
are used for fixed and mobile radio communication, broadcasting, radar and
other navigation systems, satellite communication, computer networks and
innumerable other applications. Different frequencies of radio waves have
different propagation characteristics in the Earth's atmosphere; long
waves may cover a part of the Earth very consistently, shorter waves can
reflect off the ionosphere and travel around the world, and much shorter
wavelengths bend or reflect very little and travel on a line of sight.

Short wavelengthHigh frequencyHigh energy

Long wavelengthLow frequencyLow energy

Radio waves have the
longest wavelengths in the electromagnetic spectrum. These waves can be
longer than a football field or as short as a football. Radio waves do
more than just bring music to your radio. They also carry signals for your
television and cellular phones.

The antennae on your
television set receive the signal, in the form of electromagnetic waves,
that is broadcasted from the television station. It is displayed on your
television screen.

The most common radio band
names and their corresponding wavelengths/frequencies are:

Band

Wavelength

Frequency

P-band

90 cm

327 MHz

L-band

20 cm

1.4 GHz

C-band

6.0 cm

5.0 GHz

X-band

3.6 cm

8.5 GHz

U-band

2.0 cm

15 GHz

K-band

1.3 cm

23 GHz

Q-band

7 mm

45 GHz

Cable companies have
antennae or dishes which receive waves broadcasted from your local TV
stations. The signal is then sent through a cable to your house.

How Radio Communication
Works

Sound and radio
waves are different phenomena. Sound consists of pressure
variations in matter, such as air or water. Sound will not travel through
a vacuum. Radio waves, like visible light, infrared, ultraviolet, X-rays
and gamma rays, are electromagnetic waves that do travel through
a vacuum. When you turn on a radio you hear sounds because the transmitter
at the radio station has converted the sound waves into electromagnetic
waves, which are then encoded onto an electromagnetic wave in the radio
frequency range (generally in the range of 500-1600 kHz for AM stations,
or 86-107 MHz for FM stations). Radio electromagnetic waves are used
because they can travel very large distances through the atmosphere
without being greatly attenuated due to scattering or absorption. Your
radio receives the radio waves, decodes this information, and uses a
speaker to change it back into a sound wave. An animated illustration of
this process is given below (mouse-over the images for animations).

A sound wave is
produced with a frequency of 5 Hz - 20 kHz.

The sound wave is
equivalent to a pressure wave traveling through the air.

A microphone
converts the sound wave into an electrical signal.

The electrical wave
traveling through the microphone wire is analogous to the original
sound wave.

The electrical wave
is used to encode or modulate a high-frequency "carrier" radio wave.
The carrier wave itself does not include any of the sound
information until it has been modulated.

The carrier wave can
either be amplitude modulated (AM, top) by the electrical signal, or
frequency modulated (FM, bottom).

The signal is
transmitted by a radio broadcast tower.

Your radio contains
an antenna to detect the transmitted signal, a tuner
to pick out the desired frequency, a demodulator to
extract the original sound wave from the transmitted signal, and an
amplifier which sends the signal to the speakers. The speakers
convert the electrical signal into physical vibrations (sound).

Credit:NASA, ESA, The National Radio
Astronomy Observatory

Data compiled from The
British Antarctic Study, NASA, Environment Canada, UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated daily This Website is a project of the The Ozooe Hole
Inc. http://www.theozonehole.com